1. Technical Field
The present invention relates to a clutch device. More specifically, the present invention relates to a clutch device driven by hydraulic pressure.
2. Background Information
A torque converter is a device for transmitting power via fluid inside of a torus having three types of runners (an impeller, a turbine, and a stator). The impeller forms a fluid chamber, in which operating oil is filled, with a front cover. The impeller mainly includes an annular impeller shell, a plurality of impeller blades fixed inside of the annular impeller shell, and an annular impeller core fixed inside of the impeller blades. The turbine is disposed in the fluid chamber opposite to the impeller in an axial direction. The turbine mainly includes an annular turbine shell, a plurality of turbine blades fixed on the surface of the turbine shell facing towards the impeller, and an annular turbine core fixed inside of the turbine blades. The inner periphery portion of the turbine shell is fixed to the flange of a turbine hub by a plurality of rivets. The turbine hub is coupled with an input shaft and is unrotatable. The stator is a mechanism to regulate flow of the operating oil returning to the impeller from the turbine and is disposed between the inner periphery portion of the impeller and the inner periphery portion of the turbine. The stator mainly includes an annular stator shell, a plurality of stator blades provided on the outer surface of the annular stator shell, and an annular stator core fixed at the end of the plurality of stator blades. The annular stator shell is supported by a fixing shaft via a one-way clutch.
Generally, the torque converter enables smooth acceleration and deceleration by transmitting power via fluid. However, the slippage of fluid causes energy loss and low fuel efficiency.
Accordingly, some torque converters have included a lock-up device disposed in a space between the front cover and the turbine that mechanically couples the front cover on the input side and the turbine on the output side. The lock-up device mainly includes a disc-like piston which can be pressed against the front cover, a driven plate attached to the back surface side of the turbine, and a torsion spring elastically coupling the piston and the driven plate in a rotational direction. The piston has an annular friction member adhered to a position opposed to a flat friction surface of the front cover, as shown in Japanese Unexamined Patent Publication No. 2004-100714
On the other hand, a multi-staged transmission reduces the need for the function to increase torque ratio provided in the torque converter. That is to say, even if a usual friction clutch without the function to increase torque ratio is used instead of the torque converter, the multi-staged transmission allows the vehicle to secure smooth start performance.
In such a case, the friction clutch for starting is provided in an automatic transmission instead of the torque converter. However, since the known torque converter is controlled by the hydraulic circuit with two oil passages, a friction clutch is also required to be controllable through only two oil passages in order to be attached.